Driving assistance apparatus

ABSTRACT

A driving assistance apparatus predicts an appropriate operation amount which is an operation amount performed by a driver in correspondence with the external environment, and sets the appropriate operation amount range including the appropriate operation amount, an appropriate operation amount range including the appropriate operation amount, and changes the reaction force characteristics of the operation device when it is determined that the operation amount of the driver corresponding to the prediction time point of the appropriate operation amount is not included in the appropriate operation amount range.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.16/396,869 filed on Apr. 29, 2019 (allowed), which claims the benefit ofpriority from Japanese Patent Application No. 2018-107751, filed Jun. 5,2018. The entire disclosures of the prior applications are consideredpart of the disclosure of the accompanying continuation application, andare hereby incorporated by reference.

TECHNICAL FIELD

The present disclosure relates to a driving assistance apparatus.

BACKGROUND

In the related art, Japanese Unexamined Patent Publication No.2003-063430 is known as a technical literature relating to a drivingassistance apparatus. In this publication, there is described anapparatus that estimates a driving operation amount required for adriver in the future, and controls the operation of vehicle's equipmentso as to prompt the necessary driving operation amount for the driver.

SUMMARY

However, when an operation interference is performed so as to prompt thenecessary driving operation amount for the driver, this leads to adeterioration in the sense of initiative of the driver in the drivingoperation. For this reason, it is required to provide a drivingassistance such that the operation amount of the driver becomesappropriate while maintaining the sense of initiative of the driver.

An aspect of the present disclosure provides a driving assistanceapparatus that assists a driving operation of a vehicle by a driver, theapparatus includes: an operation amount recognition unit configured torecognize an operation amount of the driver for the operation device ofthe vehicle; an operation history storage unit configured to store anoperation history which is a history of the operation amount of thedriver; an external environment recognition unit configured to recognizean external environment of the vehicle; an appropriate operation amountprediction unit configured to predict an appropriate operation amountwhich is the operation amount performed by the driver in correspondencewith the external environment, based on the operation history of thedriver and the external environment; an appropriate operation amountrange setting unit configured to set an appropriate operation amountrange including the appropriate operation amount when the appropriateoperation amount is predicted by the appropriate operation amountprediction unit; a determination unit configured to determine whether ornot the operation amount of the driver corresponding to a predictiontime point of the appropriate operation amount is included in theappropriate operation amount range; and a reaction force characteristicschange unit configured to change reaction force characteristics of theoperation device such that a reaction force increase amount with respectto the increase of the operation amount in the appropriate operationamount range is large compared to the reaction force increase amountwith respect to the increase of the operation amount from the operationamount at the time of the determination to the appropriate operationamount range, or such that the reaction force decrease amount withrespect to the decrease of the operation amount in the appropriateoperation amount range is large compared to the reaction force decreaseamount with respect to the decrease of the operation amount from theoperation amount at the time of the determination to the appropriateoperation amount range, when it is determined by the determination unitthat the operation amount of the driver corresponding to the predictiontime point of the appropriate operation amount is not included in theappropriate operation amount range.

In the driving assistance apparatus according to an aspect of thepresent discloser, when it is determined that the operation amount ofthe driver corresponding to the prediction time point for theappropriate operation amount is not included in the appropriateoperation amount range, the reaction force characteristics of theoperation device is changed such that the reaction force increase amountwith respect to the increase of operation amount in the appropriateoperation amount range is large compared to the reaction force increaseamount with respect to the increase of the operation amount from theoperation amount at the time of determination to the appropriateoperation amount range. In this case, since the reaction force increaseamount with respect to the increase of the operation amount becomeslarge when the operation amount of the driver enters the appropriateoperation amount range, it is possible to prevent the driver fromincreasing the force required for further operation and causing theoperation amount of the driver to exceed the appropriate operationamount range, and thus, it is possible to make the operation amount ofthe driver easy to stay in the appropriate operation amount range.

Alternatively, in the driving assistance apparatus, when it isdetermined that the operation amount of the driver corresponding to theprediction time point for the appropriate operation amount is notincluded in the appropriate operation amount range, the reaction forcecharacteristics of the operation device is changed such that thereaction force decrease amount with respect to the decrease of operationamount in the appropriate operation amount is large compared to thereaction force decrease amount with respect to the decrease of theoperation amount from the operation amount at the time of determinationto the appropriate operation amount range. In this case, since thereaction force decrease amount with respect to the decrease of theoperation amount becomes large when the operation amount of the driverenters the appropriate operation amount range, and the reaction forcethat boosts the operation amount of the driver decreases, it is possibleto prevent the operation amount of the driver from exceeding theappropriate operation amount range, and thus, it is possible to make theoperation amount of the driver easy to stay in the appropriate operationamount range. Furthermore, in the driving assistance apparatus, since itis easy for the operation amount of the driver to stay in theappropriate operation amount range by changing the reaction forcecharacteristics of the operation device, it is possible to maintain thesense of initiative of the driver compared to the case where theoperation amount of the driver is forcibly interfered so as to becomethe appropriate operation amount. Therefore, driving assistanceapparatus, it is possible to perform the driving assistance such thatthe operation amount of the driver can be appropriate while maintainingthe sense of initiative of the driver.

In the driving assistance apparatus according to an aspect of thepresent disclosure, the operation amount recognition unit may beconfigured to recognize a steering amount of the driver for a steeringdevice of the vehicle as the operation amount of the driver for theoperation device, the appropriate operation amount prediction unit maybe configured to predict an appropriate steering amount as theappropriate operation amount, the appropriate operation amount rangesetting unit may be configured to set an appropriate steering amountrange as the appropriate operation amount range, the determination unitmay be configured to determine whether or not the steering amount of thedriver corresponding to the prediction time point of the appropriatesteering amount is included in the appropriate steering amount range,and the reaction force characteristics change unit is configured tochange the reaction force characteristics of the steering device, suchthat the reaction force increase amount with respect to the increase ofthe steering amount in the appropriate operation amount range is largecompared to the reaction force increase amount with respect to theincrease of the steering amount from the steering amount at the time ofthe determination which is the steering amount at the time ofdetermination to the appropriate operation amount range, or such thatthe reaction force decrease amount with respect to the decrease of thesteering amount in the appropriate steering amount range is largecompared to the reaction force decrease amount with respect to thedecrease of the steering amount from the steering amount at the time ofthe determination to the appropriate steering amount range, when it isdetermined by the determination unit that the steering amount of thedriver corresponding to the prediction time point of the appropriatesteering amount is not included in the appropriate steering amountrange.

Another aspect of the present disclosure provides a driving assistanceapparatus that assists a driving operation of a vehicle by a driver, theapparatus includes: an operation amount recognition unit configured torecognize an operation amount of the driver for an operation device ofthe vehicle; an operation history storage unit configured to store anoperation history which is a history of the operation amount of thedriver; an external environment recognition unit configured to recognizean external environment of the vehicle; an appropriate operation amountprediction unit configured to predict an appropriate operation amountwhich is the operation amount performed by the driver in correspondencewith the external environment, based on the operation history of thedriver and the external environment; an appropriate operation amountrange setting unit configured to set an appropriate operation amountrange including the appropriate operation amount when the appropriateoperation amount is predicted by the appropriate operation amountprediction unit; a determination unit configured to determine whether ornot the operation amount of the driver corresponding to a predictiontime point of the appropriate operation amount is included in theappropriate operation amount range; and a reaction force characteristicschange unit configured to change reaction force characteristics of theoperation device to reaction force characteristics for maintaining thesense of initiative with which the operation amount of the driver amountcan easily remain in the appropriate operation amount range byperforming a minute change on the reaction force characteristics of theoperation device when it is determined by the determination unit thatthe operation amount is included in the appropriate operation amountrange, when it is determined by the determination unit that theoperation amount of the driver corresponding to the prediction timepoint of the appropriate operation amount is not included in theappropriate operation amount range.

According to the driving assistance apparatus, when it is determinedthat the operation amount of the driver amount corresponding to theprediction time point for the appropriate operation amount is notincluded in the appropriate operation amount range, it is possible tomake the operation amount of the driver remain in the appropriateoperation amount range by changing the reaction force characteristics tothe reaction force characteristics for maintaining the sense ofinitiative in which the operation amount of the driver is likely to stayin the appropriate operation amount range by performing the minutechange on the reaction force characteristics of the operation device. Inaddition, in the driving assistance apparatus, since it is easy for theoperation amount of the driver to stay in the appropriate operationamount range by changing the reaction force characteristics of theoperation device, it is possible to make the operation amount of thedriver appropriate while maintaining the sense of initiative of thedriver compared to the case where the operation amount of the driver isforcibly interfered so as to become the appropriate operation amount.

The driving assistance apparatus in another aspect of the presentdisclosure may further include a curve traveling recognition unitconfigured to determine whether or not the vehicle is traveling on acurve. The operation amount recognition unit may be configured torecognize a steering amount of the driver for the steering device of thevehicle as the operation amount of the driver for the operation device,the appropriate operation amount prediction unit may be configured topredict an appropriate steering amount as the appropriate operationamount, the appropriate operation amount range setting unit may beconfigured to set an appropriate steering amount range as theappropriate operation amount range, the determination unit may beconfigured to determine whether or not the steering amount of the drivercorresponding to the prediction time point of the appropriate steeringamount is included in the appropriate steering amount range, and when itis determined by the determination unit that the steering amount of thedriver corresponding to the prediction time point of the appropriatesteering amount is not included in the appropriate operation amountrange and when it is determined by the curve traveling recognition unitthat the vehicle is traveling on the curve, the reaction forcecharacteristics change unit may be configured to change the reactionforce characteristics of the steering device to the reaction forcecharacteristics for maintaining the sense of initiative.

According to various aspects of the present disclosure, it is possibleto perform the driving assistance such that the operation amount of thedriver amount becomes appropriate while maintaining the sense ofinitiative of the driver.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a driving assistance apparatusaccording to an embodiment.

FIG. 2A is a diagram for explaining reaction force generated when asteering device is rotated from a reference position.

FIG. 2B is a diagram for explaining reaction force generated when thesteering device is rotated so as to return to the reference position.

FIG. 3 is a graph illustrating reaction force characteristics when thesteering device is rotated so as to leave from the reference position.

FIG. 4 is a graph illustrating reaction force characteristics when thesteering device is rotated so as to return to the reference position.

FIG. 5 is a graph for explaining the amount of change of reaction forcecharacteristics from the reference reaction force characteristics to thereaction force characteristics for maintaining the sense of initiative.

FIG. 6A is a graph illustrating reaction force characteristics when anaccelerator pedal is pressed.

FIG. 6B is a graph illustrating reaction force characteristics when theaccelerator pedal is released.

FIG. 7A is a graph illustrating reaction force characteristics when abrake pedal is pressed.

FIG. 7B is a graph illustrating reaction force characteristics when thebrake pedal is released.

FIG. 8 is diagrams for explaining a functional outline of the drivingassistance apparatus.

FIG. 9 is a flowchart illustrating an example of reaction forcecharacteristics change processing.

FIG. 10 is a flowchart illustrating an example of reaction force controlprocessing.

DETAILED DESCRIPTION

Hereinafter, an embodiment of the present disclosure will be describedwith reference to the drawings.

FIG. 1 is a block diagram illustrating a driving assistance apparatusaccording to an embodiment. A driving assistance apparatus 100 accordingto an embodiment illustrated in FIG. 1 performs driving assistance tochange reaction force characteristics of an operation device T such thata operation amount of the driver to the operation device T of a vehiclebecomes an appropriate operation amount. The driving assistanceapparatus 100 performs the driving assistance while maintaining thesense of initiative of the driver by minor change of the reaction forcecharacteristics.

Configuration of Driving Assistance Apparatus

As illustrated in FIG. 1 , the driving assistance apparatus 100 includesan electronic control unit (ECU) 10 that performs an overall managementof the apparatus. The ECU 10 is an electronic control unit including acentral processing unit (CPU), read only memory (ROM), random accessmemory (RAM), a controller area network (CAN) communication circuit, andthe like. In the ECU 10, for example, various functions are realized byloading a program stored in the ROM into the RAM and executing theprogram loaded in the RAM by the CPU. In the ECU 10, for example,various functions are realized by loading a program stored in the ROMinto the RAM and executing the program loaded in the RAM by the CPU.

The ECU 10 is connected to a GPS receiver 1, an external sensor 2, aninternal sensor 3, a driving operation detection unit 4, a map database5, operation history storage unit 6, a proportional integraldifferential (PID) controller 7, and a reaction force actuator 8.

The GPS receiver 1 measures a position of the vehicle (for example,latitude and longitude of the vehicle) by receiving signals from equalto or more than three GPS satellites. The GPS receiver 1 transmitsinformation on the measured position of the vehicle to the ECU 10.

The external sensor 2 is a detection device that detects a surroundingenvironment of the vehicle. The external sensor 2 includes at least oneof a camera and a radar sensor.

The camera is an imaging device that images the external situation ofthe vehicle. The camera is provided on at the inside of a windshield ofthe vehicle. The camera transmits image information relating tosurroundings of the vehicle to the ECU 10. The camera may be a monocularcamera or may be a stereo camera.

The radar sensor is a detection device that detects obstacles around thevehicle using radio waves (for example, millimeter waves) or light. Theradar sensor includes, for example, millimeter wave radar or a lightdetection and ranging (LIDAR). The radar sensor transmits the radio waveor light to the surroundings of the vehicle, and detects the obstaclesby receiving radio waves or light reflected from obstacles. The radarsensor transmits the detected object information to the ECU 10.

The internal sensor 3 is a detection device that detects a travel stateand a vehicle state of the vehicle. The internal sensor 3 includes avehicle speed sensor, an accelerator sensor, and a yaw rate sensor. Thevehicle speed sensor is a measurement device that measures a speed ofthe vehicle. As the vehicle speed sensor, for example, a vehicle wheelspeed sensor is used, which is provided on vehicle wheels of the vehicleor on a drive shaft rotating integrally with vehicle wheels, andmeasures a rotational speed of the vehicle wheels. The vehicle speedsensor transmits the measured vehicle speed information (vehicle wheelspeed information) to the ECU 10.

The accelerator sensor is a measurement device that measures anacceleration of the vehicle. The accelerator sensor includes, forexample, a longitudinal accelerator sensor that measures acceleration inthe longitudinal direction of the host vehicle V and a lateralaccelerator sensor that measures a lateral acceleration of the hostvehicle. The accelerator sensor transmits, for example, accelerationinformation of the vehicle to the ECU 10. The yaw rate sensor is ameasurement device that measures a yaw rate (rotation angular velocity)around the vertical axis at the center of gravity of the vehicle. As theyaw rate sensor, for example, a Gyro sensor can be used. The yaw ratesensor transmits the measured yaw rate information of the vehicle to theECU 10.

The driving operation detection unit 4 detects the operation amount ofthe driver of the operation device T of the vehicle. The operationdevice T of the vehicle is equipment to which the driver inputs theoperation for driving the vehicle. The operation device T of the vehicleincludes at least one of a steering device of the vehicle, anaccelerator operation device of the vehicle, and a brake operationdevice of the vehicle.

The steering device is, for example, a steering wheel. The steeringdevice is not limited to a case of wheel-shape, but may be anyconfiguration as long as the section functions as a steering wheel. Theaccelerator operation device is, for example, an accelerator pedal. Thebrake operation device is, for example, a brake pedal. The acceleratoroperation device and the brake operation device do not necessarily needto be pedals, but may be any configurations as long as the driver caninput the acceleration or the deceleration.

In addition, the operation device T of the vehicle has a referenceposition. The reference position is an initial state of the operationdevice T, and when the driver does not perform the operation, theoperation device T is configured to return to the reference position.The operation device T is configured to generate reaction forceaccording to an amount of change (an operation amount) when thereference position is changed by the driver's operation. When the driveroperates the operation devices T so as to return to the referenceposition, the operation device T generates the reaction force (restoringforce) so as to activate the driver's operation.

FIG. 2A is a diagram for explaining the reaction force generated whenthe steering device ST is rotated from a reference position. Thesteering device ST illustrated in FIG. 2A is in a state of referenceposition. As illustrated in FIG. 2A, when the driver rotates thesteering device ST counterclockwise from the reference position, thereaction force is generated in the steering device ST so as to hinderthe rotation by the driver. FIG. 2B is a diagram for explaining thereaction force generated when the steering device ST is rotated so as toreturn to the reference position. The steering device ST illustrated inFIG. 2B is rotated leftward from the reference position. In FIG. 2B, thedriver rotates the steering device ST such that the steering device STreturns to the reference position. In this case, as illustrated in FIG.2B, the reaction force is generated in steering device ST such that therotation by driver is boosted (activated). The reaction force has beendescribed with the steering device ST as an example, and also in theaccelerator operation device and the brake operation device, thereaction force is generated such that each operation device returns tothe reference position (for example, the initial position of the pedal).

The driving operation detection unit 4 includes at least one of asteering sensor, an accelerator sensor, and a brake sensor. The steeringsensor measures the operation amount of the steering device by driver.The operation amount of the steering device includes a steering angle.The operation amount of the steering device may include a steeringtorque. The accelerator sensor measures the operation amount of theaccelerator operation device by the driver. The operation amount of theaccelerator operation device includes, for example, a pedal stroke(amount of pressing) of the accelerator pedal. The brake sensor measuresthe operation amount of the brake operation device by the driver. Theoperation amount of the brake operation device includes, for example, apedal stroke (amount of pressing) of the brake pedal. The operationamount of the accelerator operation device and the brake operationdevice may include a pressing speed. The driving operation detectionunit 4 transmits the operation amount information on the measuredoperation amount of the driver to the ECU 10.

The map database 5 is a database storing map information. The mapdatabase 5 is formed, for example, in a hard disk drive (HDD) mounted onthe vehicle. The map information includes information on the position ofthe road, information on the shape of the road (for example, types ofcurves or straight roads, a curvature of the curve, or the like),information on the position of the intersection and the branch, andinformation on the position of a structure. The map information may alsoinclude traffic regulation information such as a speed limit associatedwith the position information. The map database 5 does not to be mountedon the vehicle, but may be stored in a server that can communicate withthe vehicle.

The operation history storage unit 6 is a database that stores aoperation history of the driver. The operation history storage unit 6 isconfigured in, for example, the HDD mounted on the vehicle. Theoperation history of the driver is a history of the operation amount ofthe driver.

The operation history storage unit 6 stores the operation amount of thedriver history after the travel start of the vehicle. The operationhistory storage unit 6 may store the operation history of the driverseparately for each trip of the vehicle. If a function of personaldriver authentication is installed in the vehicle, the operation historystorage unit 6 may store a past operation history for each individualpersonal authenticated driver. The operation history storage unit 6 maystore all the operation history of the driver who drives the vehicle(operation history that does not distinguish the drivers from eachindividual), without performing the personal authentication. Inaddition, the operation history storage unit 6 may store the operationhistory of the driver in association with the external environment andthe vehicle state of the vehicle at the time of operation. Details ofthe external environment and the vehicle state will be described later.The operation history storage unit 6 does not need to be mounted on thevehicle, but may be formed in a server that can communicate with thevehicle.

The PID controller 7 is a controller that performs PID control on thereaction force of the operation device T of the vehicle. The PIDcontroller 7 calculates a command value from a control signal from theECU 10 according to the operation amount of the driver and the result ofcontrol of the vehicle, and transmits the command value to the reactionforce actuator 8. In this way, the PID controller 7 suppresses theinfluence of the disturbance such as the road surface condition to theoperation device T.

The reaction force actuator 8 is an actuator that controls the reactionforce of the operation device T of the vehicle. The reaction forceactuator 8 is connected to the ECU 10 via the PID controller 7. Thereaction force actuator 8 includes at least one of a steering reactionforce actuator, an accelerator reaction force actuator, and a brakereaction force actuator.

The steering reaction force actuator controls the reaction force of thesteering device of the vehicle. The steering reaction force actuator isan electric motor that is, for example, provided on a steering shaft andapplies the reaction force (torque) to the steering device through thesteering shaft. As the steering reaction force actuator, an electricpower steering (EPS) motor may be used. As the steering reaction forceactuator, an actuator in a steer-by-wire system in the steering devicemay be used. The steering reaction force actuator does not need tooutput all of the reaction force, but may adjust the reaction force feltby the driver by changing the output in combination with the reactionforce mechanically transmitted from the tire. The steering reactionforce actuator gives the reaction force to the steering device based onthe command value transmitted from the PID controller 7.

The accelerator reaction force actuator controls the reaction force ofthe accelerator operation device of the vehicle. The acceleratorreaction force actuator is an electric motor provided, for example, onthe accelerator pedal, and gives the reaction force to the acceleratorpedal. The accelerator reaction force actuator gives the reaction forceto the accelerator pedal (accelerator operation device) based on thecommand value transmitted from PID controller 7. The brake reactionforce actuator controls the reaction force of the brake operation deviceof the vehicle. The brake reaction force actuator is an electric motorprovided on, for example, the brake pedal, and gives the reaction forceto the brake pedal. The brake reaction force actuator gives the reactionforce to the brake pedal (brake operation device) based on the commandvalue transmitted from the PID controller 7.

Next, a functional configuration of the ECU 10 will be described. TheECU 10 includes a vehicle position recognition unit 11, an externalenvironment recognition unit 12, a vehicle state recognition unit 13, acurve traveling recognition unit 14, an operation amount recognitionunit 15, an appropriate operation amount prediction unit 16, anappropriate operation amount range setting unit 17, a determination unit18, a reaction force characteristics change unit 19, and a reactionforce control unit 20. A part of the functions of the ECU 10 describedbelow may be performed in a server that can communicate with thevehicle.

The vehicle position recognition unit 11 recognizes a vehicle positionon the map based on the position information from the GPS receiver 1 andthe map information in the map database 5. In addition, the vehicleposition recognition unit 11 may recognize the vehicle position on themap using the position information on fixed obstacles such as utilitypoles included in the map information in the map database 5 and theresult of detection performed by the external sensor 2 using asimultaneous localization and mapping (SLAM) technology. The vehicleposition recognition unit 11 may recognize the vehicle position on themap using a well-known method.

The external environment recognition unit 12 detects an externalenvironment of the vehicle based on the result of detection performed bythe external sensor 2 (image captured by the camera and/or objectinformation by the radar sensor) and the vehicle position on the map andmap information recognized by the vehicle position recognition unit 11.The external environment includes road situations around the vehicle andobject situations around the vehicle.

The road situation includes the curvature of the traveling road on whichthe vehicle travels. The road situation may include slopes, lane widths,and the number of lanes. The external environment recognition unit 12can recognize the road situation from the map information and/or fromthe result of detection performed by the external sensor 2. The objectsituation includes a position of the object with respect to the vehicle.The object situation may include a moving direction of the object withrespect to the vehicle and a relative speed of the object with respectto the vehicle. The external environment recognition unit 12 canrecognize the object situation from the result of detection performed bythe external sensor 2.

The vehicle state recognition unit 13 recognizes the state of thetraveling vehicle based on the result of measurement performed by theinternal sensor 3. The vehicle state includes at least one of a vehiclespeed of the vehicle, an acceleration of the vehicle, and a yaw rate ofthe vehicle. The vehicle state recognition unit 13 can recognize thevehicle speed of the vehicle based on the vehicle speed information fromthe vehicle speed sensor. The vehicle state recognition unit 13 canrecognize the acceleration (a longitudinal acceleration and a lateralacceleration) of the vehicle based on the acceleration information fromthe accelerator sensor. The vehicle state recognition unit 13 canrecognize the yaw rate of the vehicle based on the yaw rate informationfrom the yaw rate sensor.

The curve traveling recognition unit 14 determines whether or not thevehicle is traveling on a curve. The curve traveling recognition unit 14determines whether or not the vehicle is traveling on a curve based onthe curvature of the traveling road recognized by external environmentrecognition unit 12.

The operation amount recognition unit 15 recognizes the operation amountof the driver on the operation device T of the vehicle based on theoperation amount information from the driving operation detection unit4. The operation amount recognition unit 15 recognizes at least one ofthe steering amount of the driver on the steering device of the vehicle,the driver's accelerator operation amount on the accelerator operationdevice of the vehicle, and the driver's brake operation amount on thebrake operation device of the vehicle, as the operation amount of thedriver. The operation amount recognition unit 15 may store the result ofrecognizing the operation amount of the driver in the operation historystorage unit 6.

The appropriate operation amount prediction unit 16 predicts aappropriate operation amount of the driver based on the operationhistory of the driver stored in the operation history storage unit 6,the external environment recognized by the external environmentrecognition unit 12, and the vehicle state recognized by the vehiclestate recognition unit 13. For example, at least the operation historyfrom the current time point to a certain time before can be used as theoperation history of the driver. A certain time is, for example, severalseconds.

The appropriate operation amount is an operation amount that the drivernormally tries to operate corresponding the external environment alongthe operation history of the driver. The appropriate operation amount ispredicted as the operation amount when it is assumed that the drivergrasps the external environment and the vehicle state based on theoperation history of the driver, external environment, and the vehiclestate, and performs the appropriate driving operation. As an example,the appropriate operation amount can be an operation amount in which thevehicle travels in the vicinity of the center of the driving lane andthe distance between the vehicle and the surrounding object such as apreceding vehicle can be secured as equal to or longer than a certaindistance. The appropriate operation amount includes at least one of anappropriate steering amount corresponding to the steering amount, anappropriate accelerator operation amount corresponding to theaccelerator operation amount, and an appropriate brake operation amountcorresponding to the brake operation amount.

The appropriate operation amount prediction unit 16 predicts theappropriate operation amount at a prediction time point set in advance.The prediction time point is a time point at which the appropriateoperation amount is predicted. The prediction time point can be, forexample, 0.5 seconds, 1 second, and 2 seconds after the current timepoint. The prediction time point may be a time point after a lapse of atime longer than a certain time considering the processing cycle of thevehicle such that the time point does not become a past time at the timeof performing the control.

As an example, the appropriate operation amount prediction unit 16predicts the appropriate operation amount using a driving behavior modeloptimized by machine learning. The driving behavior model is generatedin such a manner that the appropriate operation amount is output at theprediction time point when the operation history of the driver, theexternal environment, and the vehicle state are input. The appropriateoperation amount prediction unit 16 may predict the appropriateoperation amount using a statistical model. From vast statistical datain which the operation history of the driver, the external environment,and the vehicle state, and the subsequent operation amount of the driverare associated with each other, the appropriate operation amountprediction unit 16 searches for a case having the similar operationhistory of the driver, the external environment, and the vehicle state,and then, the operation amount of the driver can be predicted using theappropriate operation amount in the similar case. The statistical datais stored in, for example, a server that can communicate with thevehicle. The method of predicting the appropriate operation amount bythe appropriate operation amount prediction unit 16 is not particularlylimited, and various methods can be adopted. The appropriate operationamount prediction unit 16 may predict the appropriate operation amountusing a driving trend of a driver instead of the operation history ofthe driver. The driver's driving trend can be obtained from theoperation history of the driver using a well known evaluation method.

When the appropriate operation amount is predicted by the appropriateoperation amount prediction unit 16, the appropriate operation amountrange setting unit 17 sets an appropriate operation amount rangeincluding the appropriate operation amount. The appropriate operationamount range is a range of the operation amount including theappropriate operation amount. The appropriate operation amount range maybe set as a range with the appropriate operation amount as a medianvalue. The appropriate operation amount range can be set as a certainrange set in advance. The appropriate operation amount range does notnecessarily need to be the median value of the appropriate operationamount, and the appropriate operation amount may be a value deviatedfrom the median value.

The appropriate operation amount range includes at least one of anappropriate steering amount range corresponding to the appropriatesteering amount, an appropriate accelerator operation amount rangecorresponding to the appropriate accelerator operation amount, and anappropriate brake operation amount range corresponding to theappropriate brake operation amount. As a specific example, theappropriate steering amount range can be a range of equal to or largerthan −10 degrees and equal to or smaller than +10 degrees with aclockwise steering as a positive steering angle and with the appropriatesteering amount as a median value. The appropriate steering amount rangemay be a range of equal to or larger than −5 degrees and equal to orsmaller than +5 degrees with the appropriate steering amount as a medianvalue. Regarding the appropriate accelerator operation amount range, acertain accelerator operation amount range with the appropriateaccelerator operation amount as a median value can be the appropriateaccelerator operation amount range. The same is true for the case ofappropriate brake operation amount range.

The determination unit 18 determines whether or not the operation amountof the driver corresponding to the prediction time point for theappropriate operation amount is included in the appropriate operationamount range based on the operation amount of the driver recognized bythe operation amount recognition unit 15 and the appropriate operationamount range set by the appropriate operation amount range setting unit17.

The operation amount of the driver corresponding to the prediction timepoint for the appropriate operation amount is the operation amount ofthe driver recognized at the prediction time point, for example. As theoperation amount of the driver amount corresponding to the predictiontime point for the appropriate operation amount, the operation amount ofthe driver recognized immediately before the prediction time point (forexample, the recognition timing of the previous operation amount) may beused. Hereinafter, the operation amount of the driver amount when theoperation amount of the driver amount corresponding to the predictiontime point for the appropriate operation amount is determined not to beincluded in the appropriate operation amount range is referred to as anoperation amount at the time of determination. The operation amount atthe time of determination includes at least one of a steering amount atthe time of determination, an accelerator operation amount at the timeof determination, and a brake operation amount at the time ofdetermination.

When it is determined by the determination unit 18 that the operationamount of the driver amount corresponding to the prediction time pointfor the appropriate operation amount is not included in the appropriateoperation amount range and when it is determined by the curve travelingrecognition unit 14 that the vehicle is traveling on a curve, thereaction force characteristics change unit 19 changes the reaction forcecharacteristics of the operation device T to the reaction forcecharacteristics for maintaining the sense of initiative.

The reaction force characteristics change unit 19 can change thereaction force characteristics using, for example, a virtual modeloptimized by machine learning. When the types of operation device T (thetypes of the steering device, the accelerator operation device, and thebrake operation device), the appropriate operation amount, the operationamount of the driver, and the current operation amount are input, thevirtual model outputs the reaction force characteristics for maintainingthe sense of initiative. At least one of the reference reaction forcecharacteristics of the operation device T and the appropriate operationamount range may be included in the input to the virtual model. Byselecting any one of the type of operation device T, the appropriateoperation amount, and the appropriate operation amount range from theprepared reaction force characteristics for maintaining the sense ofinitiative patterns, the reaction force characteristics change unit 19may change the reaction force characteristics to the reaction forcecharacteristics for maintaining the sense of initiative. The reactionforce characteristics change unit 19 may use a physical model, amathematical model, or a statistical model. The method of changing thereaction force characteristics using the reaction force characteristicschange unit 19 is not particularly limited, and various methods can beadopted.

The reaction force characteristics of the operation device T is thecharacteristics of the reaction force given to the operation device Taccording to the operation amount of the driver for the operation deviceT. The reaction force characteristics relates to the amount of change ofthe reaction force according to the change of the operation amount ofthe driver for the operation device T. The reaction forcecharacteristics relates to force sensing characteristics felt by thedriver from the operation device T.

Here, the reaction force characteristics of the operation device T whenit is determined by the determination unit 18 that the operation amountof the driver amount corresponding to the prediction time point for theappropriate operation amount is included in the appropriate operationamount range is referred to as reference reaction force characteristics.The reaction force characteristics for maintaining the sense ofinitiative can be set by performing a minute change on the referencereaction force characteristics. The minute change means a change of suchan extent that the sense of initiative of the driver can be maintained.

The reaction force characteristics for maintaining the sense ofinitiative means reaction force characteristics in which the operationamount of the driver is likely to stay in the appropriate operationamount range while maintaining the sense of initiative of the driver.The sense of initiative of the driver is the sense of initiative for thedriver's driving operation of the vehicle. The sense of initiative ofthe driver relates to the driver's willingness to the driving operation.Excessive operation intervention on the driver's driving operationdecreases the driver's willingness to the driving operation and impairsthe sense of initiative.

The reaction force characteristics for maintaining the sense ofinitiative can be defined as the reaction force characteristics in whicha reaction force increase amount with respect to the increase of theoperation amount in the appropriate operation amount range is largecompared to a reaction force increase amount with respect to theincrease of the operation amount from the operation amount at the timeof determination that the operation amount of the driver is not includedin the appropriate operation amount range to the appropriate operationamount range. “When the reaction force increases with respect to thechange in the operation amount” means a time when the operation deviceis operated to leave from the reference position. Specifically, a casewhere the driver rotates the steering device in one direction so as toleave from the reference position (reference angle) is included. Inaddition, a case where the driver is pressing the accelerator pedal orthe brake pedal from the reference position is included.

In this case, while changing the operation amount for the operationdevice T so as to approach the appropriate operation amount (forexample, the operation amount according to the curvature of the curve onwhich the vehicle travels), the reaction force increase amount felt bythe driver after the operation amount reaches the appropriate operationamount range is large compared to that before the operation amountreaches the appropriate operation amount range. Therefore, the drivercan decrease the possibility of deviating beyond the appropriateoperation amount range caused by further increase of the operationamount, and thus, it is possible to make the operation amount of thedriver easy to stay in the appropriate operation amount range.

FIG. 3 is a graph illustrating the reaction force characteristics whenthe steering device ST is rotated so as to leave from the referenceposition. In FIG. 3 , the vertical axis represents the steering reactionforce and the horizontal axis represents the steering angle. Thereference position is assumed to be 0 degree. FIG. 3 illustrates anexample of the appropriate steering amount Ps, the appropriate steeringamount range Es, the reference reaction force characteristics B, and thereaction force characteristics M for maintaining the sense ofinitiative. In FIG. 3 , it is assumed that the appropriate steeringamount Ps is set to 30 degrees, and the appropriate steering amountrange Es is set to equal to or larger than 25 degrees and equal to orsmaller than 35 degree. In addition, in FIG. 3 , the vehicle is assumedto be traveling on a curve, and the current steering angle of thesteering device ST is equal to or larger than 0 degrees and equal to orsmaller than 25 degrees. That is, the current steering angle is notincluded in the appropriate steering amount range Es, and it isnecessary to increase the steering angle so as to reach the appropriatesteering amount Ps in order to leave from the reference position.

In the situation illustrated in FIG. 3 , since it is determined by thedetermination unit 18 that the steering angle (steering amount) by thedriver corresponding to the prediction time point of the appropriatesteering amount is not included in the appropriate steering amount rangeEs, and it is determined by the curve traveling recognition unit 14 thatthe vehicle is running on the curve, the reaction force characteristicschange unit 19 changes the reaction force characteristics of thesteering device ST from the reference reaction force characteristics Bto the reaction force characteristics M for maintaining the sense ofinitiative. The reaction force characteristics M for maintaining thesense of initiative is the reaction force (steering reaction force) sameas the reference reaction force characteristics B in the appropriatesteering amount Ps (30 degrees in this case). That is, the driverreceives the reaction force same as the reference reaction forcecharacteristics B when the operation amount reaches the appropriatesteering amount Ps.

The reaction force characteristics change unit 19 changes the reactionforce characteristics to the reaction force characteristics M formaintaining the sense of initiative by performing the minute change suchthat the reaction force increase amount with respect to the increase ofsteering angle in the appropriate steering amount range Es is large thanthat in the reference reaction force characteristics B. In the reactionforce characteristics M for maintaining the sense of initiative, thereaction force increase amount with respect to the increase of theoperation amount in the appropriate steering amount range Es is largecompared to the reaction force increase amount (the reaction forceincrease amount along the reference reaction force characteristics B)with respect to the increase of the steering amount from the steeringamount at the time of determination that the steering amount of thedriver is not included in appropriate steering amount range Es to timeof reaching the appropriate steering amount range Es.

The reaction force increase amount with respect to the increase of thesteering angle corresponds to the slope of the reference reaction forcecharacteristics B and the reaction force characteristics M formaintaining the sense of initiative in FIG. 3 . The reaction forcecharacteristics change unit 19 performs the minute change on thereaction force characteristics of the steering device ST to be thereaction force characteristics M for maintaining the sense of initiativein which the slope in the appropriate steering amount range Es becomesapproximately three times or twice as large as the reference reactionforce characteristics B. In the minute change, any magnification between1.1 times to 5 times may be adopted.

As illustrated in FIG. 3 , if the slope is approximately 3 times, thesteering torque increase is approximately 12%. If the slope isapproximately 2 times, the steering torque increase is approximately 7%.In the reaction force characteristics M for maintaining the sense ofinitiative, an upper limit of the increase in reaction force compared tothe reference reaction force characteristics B may be 15%. In theappropriate steering amount range Es also, the reaction forcecharacteristics is set in such a manner that the driver does not feel anexcessive burden and can change the steering amount with the driver'sintention.

Alternatively, the reaction force characteristics for maintaining thesense of initiative may be the reaction force characteristics in which areaction force decrease amount with respect to the decrease of theoperation amount in the appropriate operation amount range is largecompared to the reaction force decrease amount with respect to thedecrease of the operation amount from the operation amount at the timeof determination to the appropriate operation amount range. “When thereaction force decreases with respect to the change in the operationamount” means a time when the operation device is operated to return tothe reference position. Specifically, a case where the driver rotatesthe steering device to return to the reference position is included. Inaddition, a case where the driver weakens the pressing force on theaccelerator pedal or the brake pedal so as to return pedals to thereference position is corresponding to the case described above. At thistime, the reaction force felt by the driver is the reaction force thatboosts the driver's operation (the reaction force which makes theoperation device try to return to the reference position).

In this case, while changing the operation amount for the operationdevice T so as to approach the appropriate operation amount, thereaction force decrease amount felt by the driver after the operationamount reaches the appropriate operation amount range is large comparedto that before the operation amount reaches the appropriate operationamount range (the reaction force boosting the driver's operation becomeseasy to decrease). Therefore, the driver can decrease the possibility ofdeviating beyond the appropriate operation amount range caused byfurther increase of the operation amount, and thus, it is possible tomake the operation amount of the driver easy to stay in the appropriateoperation amount range.

Specifically, FIG. 4 is a graph illustrating the reaction forcecharacteristics when the steering device ST is rotated so as to returnto the reference position. The appropriate steering amount Ps and theappropriate steering amount range Es in FIG. 4 are the same as those inFIG. 3 . In FIG. 4 , the vehicle is assumed to be traveling on a curve,and the current steering angle of the steering device ST exceeds 35degree. That is, the current steering angle is not included in theappropriate steering amount range Es, and it is necessary to decreasethe steering angle so as to reach the appropriate steering amount Ps inorder to reach the reference position.

In the situation illustrated in FIG. 4 , since it is determined by thedetermination unit 18 that the steering angle (steering amount) by thedriver corresponding to the prediction time point of the appropriatesteering amount is not included in the appropriate steering amount rangeEs, and it is determined by the curve traveling recognition unit 14 thatthe vehicle is running on the curve, the reaction force characteristicschange unit 19 changes the reaction force characteristics of thesteering device ST from the reference reaction force characteristics Bto the reaction force characteristics M for maintaining the sense ofinitiative.

The reaction force characteristics change unit 19 changes the reactionforce characteristics to the reaction force characteristics M formaintaining the sense of initiative by performing the minute change suchthat the reaction force decrease amount with respect to the decrease ofsteering angle in the appropriate steering amount range Es is large thanthat in the reference reaction force characteristics B. In the reactionforce characteristics M for maintaining the sense of initiative, thereaction force decrease amount with respect to the decrease of theoperation amount in the appropriate steering amount range Es is largecompared to the reaction force decrease amount (the reaction forcedecrease amount along the reference reaction force characteristics B)with respect to the decrease of the steering amount from the steeringamount at the time of determination to time of reaching the appropriatesteering amount range Es.

The reaction force decrease amount with respect to the decrease of thesteering angle corresponds to the slope of the reference reaction forcecharacteristics B and the reaction force characteristics M formaintaining the sense of initiative in FIG. 4 . The reaction forcecharacteristics change unit 19 performs the minute change on thereaction force characteristics of the steering device ST to be thereaction force characteristics M for maintaining the sense of initiativein which the slope in the appropriate steering amount range Es becomesapproximately three times or twice as large as the reference reactionforce characteristics B. In the minute change, any magnification between1.1 times to 5 times may be adopted. The reaction force characteristicsM for maintaining the sense of initiative is the reaction force same asthe reference reaction force characteristics B in the appropriatesteering amount Ps (30 degrees in this case).

FIG. 5 is a graph for explaining the amount of change of reaction forcecharacteristics from the reference reaction force characteristics B tothe reaction force characteristics M for maintaining the sense ofinitiative. In FIG. 5 , the vertical axis represents the steeringreaction force and the horizontal axis represents steering angle. FIG. 5illustrates the appropriate steering amount range Es and the amount ofchange of the reaction force characteristics.

The graph illustrated in in FIG. 5 corresponds to a force sensinginteraction added to the reference reaction force characteristics B inorder to perform the minute change on the reaction force characteristicsM for maintaining the sense of initiative. The amount of change of thereaction force characteristics corresponds to the magnitude of the forcesensing interaction. As illustrated in FIG. 5 , the minute change isperformed such that the slope of the appropriate steering amount rangeEs is large. For example, the minute change can be a change that issufficiently small relative to basic reaction force characteristics (incomparing the maximum value, the change of equal to or smaller than ⅕ orthe like), or a change of such an extent that the operation device Tdoes not significantly move due to the change. The reaction forcecharacteristics change unit 19 changes the reaction forcecharacteristics to the reaction force characteristics M for maintainingthe sense of initiative by adding the minute change illustrated in inFIG. 5 to the reference reaction force characteristics B according tothe predicted appropriate steering amount Ps and the set appropriatesteering amount range Es. The reaction force characteristics change unit19 does not necessarily need to prepare and use the amount of changeillustrated in FIG. 5 in advance.

As described above, the reaction force characteristics for maintainingthe sense of initiative has been described with the case of steeringdevice ST as an example, and the same can be applied to the case ofaccelerator operation device and the brake operation device.

Here, FIG. 6A is a graph illustrating the reaction force characteristicswhen the accelerator pedal is pressed. The vertical axis in FIG. 6Arepresents the pedal reaction force, and the horizontal axis representsa pedal stroke (the amount of pressing of the pedal). The pedal reactionforce of the accelerator pedal is the force that the accelerator pedaltries to return to the reference position (the initial position of thepedal). FIG. 6A illustrates an example of reaction force characteristicsMa for maintaining the sense of initiative and reference reaction forcecharacteristics Ba in the accelerator pedal. In addition, FIG. 6Aillustrates an appropriate accelerator operation amount Pa and anappropriate accelerator operation amount range Ea. In FIG. 6A, as aprecondition, the current pedal stroke of the accelerator pedal issmaller than the appropriate accelerator operation amount Pa and is notincluded in the appropriate accelerator operation amount range Ea. Thedriver needs to press the accelerator pedal to make the operation amountreach the appropriate accelerator operation amount Pa.

In the situation illustrated in FIG. 6A, since it is determined by thedetermination unit 18 that the driver's pedal stroke corresponding tothe appropriate accelerator operation amount Pa is not included in theappropriate accelerator operation amount range Ea, the reaction forcecharacteristics change unit 19 changes the reaction forcecharacteristics of the accelerator pedal from the reference reactionforce characteristics Ba to the reaction force characteristics Ma formaintaining the sense of initiative.

The reaction force characteristics change unit 19 changes the reactionforce characteristics to the reaction force characteristics Ma formaintaining the sense of initiative by performing the minute change suchthat the reaction force increase amount with respect to the increase ofthe pedal stroke of the accelerator pedal in the appropriate acceleratoroperation amount range Ea is large compared to that in the referencereaction force characteristics Ba. In the reaction force characteristicsMa for maintaining the sense of initiative, the reaction force increaseamount with respect to the increase of the pedal stoke in theappropriate accelerator operation amount range Ea is large compared tothe reaction force increase amount (the reaction force increase amountalong the reference reaction force characteristics Ba) with respect tothe increase of the pedal stoke from the accelerator operation amount atthe time of determination that the pedal stroke of the accelerator pedalby the driver is not included in the appropriate accelerator operationamount range Ea to the time when the pedal stroke reaches theappropriate accelerator operation amount range Ea.

In the reaction force characteristics Ma for maintaining the sense ofinitiative, in order to increase the slope in the appropriateaccelerator operation amount range Ea compared to that in the referencereaction force characteristics Ba, the slope becomes smaller in therange of the pedal stroke than the appropriate accelerator operationamount range Ea, but not becomes a negative slope. That is, in thereaction force characteristics Ma for maintaining the sense ofinitiative, the pedal reaction force does not decrease due to theincrease of the pedal stroke.

FIG. 6B is a graph illustrating the reaction force characteristics whenthe accelerator pedal is released. In FIG. 6B, as a precondition, thecurrent pedal stroke of the accelerator pedal is equal to or larger thanthe appropriate accelerator operation amount Pa and exceeds theappropriate accelerator operation amount range Ea. The driver needs torelease the accelerator pedal and return the accelerator pedal to reachthe appropriate accelerator operation amount Pa by the reaction force.

In the situation illustrated in FIG. 6B also, since it is determined bythe determination unit 18 that the driver's pedal stroke correspondingto the appropriate accelerator operation amount Pa is not included inthe appropriate accelerator operation amount range Ea, the reactionforce characteristics change unit 19 changes the reaction forcecharacteristics of the accelerator pedal from the reference reactionforce characteristics Ba to the reaction force characteristics Ma formaintaining the sense of initiative.

The reaction force characteristics change unit 19 changes the reactionforce characteristics to the reaction force characteristics Ma formaintaining the sense of initiative by performing the minute change suchthat the reaction force decrease amount with respect to the decrease ofthe pedal stroke of the accelerator pedal in the appropriate acceleratoroperation amount range Ea is large compared to that in the referencereaction force characteristics Ba. In the reaction force characteristicsMa for maintaining the sense of initiative, the reaction force decreaseamount with respect to the decrease of the pedal stoke in theappropriate accelerator operation amount range Ea is large compared tothe reaction force decrease amount (the reaction force decrease amountalong the reference reaction force characteristics Ba) with respect tothe decrease of the pedal stoke from the accelerator operation amount atthe time of determination to the appropriate accelerator operationamount range Ea. That is, when the pedal stroke enters the appropriateaccelerator operation amount range Ea, the return of the acceleratorpedal becomes slow.

The reaction force decrease amount with respect to the decrease of thepedal stroke corresponds to the slope of the reference reaction forcecharacteristics Ba and the reaction force characteristics Ma formaintaining the sense of initiative in FIG. 6B. The reaction forcecharacteristics change unit 19 performs the minute change on thereaction force characteristics of the accelerator pedal to be thereaction force characteristics Ma for maintaining the sense ofinitiative in which the slope in the appropriate accelerator operationamount range Ea becomes approximately three times or twice as large asthe reference reaction force characteristics Ba. In the minute change,any magnification between 1.1 times to 5 times may be adopted. Thereaction force characteristics Ma for maintaining the sense ofinitiative is the reaction force same as the reference reaction forcecharacteristics Ba in the appropriate accelerator operation amount Pa.

FIG. 7A is a graph illustrating the reaction force characteristics whenthe brake pedal is pressed. The vertical axis in FIG. 7A represents thepedal reaction force, and the horizontal axis represents a pedal stroke(the amount of pressing of the pedal). The pedal reaction force of thebrake pedal is the force that the brake pedal tries to return to thereference position (the initial position of the pedal). FIG. 7Aillustrates an example of reaction force characteristics Mb formaintaining the sense of initiative and reference reaction forcecharacteristics Bb in the brake pedal. In addition, FIG. 7A illustratesan appropriate brake operation amount Pb and an appropriate brakeoperation amount range Eb. In FIG. 7A, as a precondition, the currentpedal stroke of the brake pedal is smaller than the appropriate brakeoperation amount Pb and is not included in the appropriate brakeoperation amount range Eb. The driver needs to press the brake pedal tomake the operation amount reach the appropriate brake operation amountPb.

In the situation illustrated in FIG. 7A, since it is determined by thedetermination unit 18 that the driver's pedal stroke corresponding tothe appropriate brake operation amount Pb is not included in theappropriate brake operation amount range Eb, the reaction forcecharacteristics change unit 19 changes the reaction forcecharacteristics of the brake pedal from the reference reaction forcecharacteristics Bb to the reaction force characteristics Mb formaintaining the sense of initiative.

The reaction force characteristics change unit 19 changes the reactionforce characteristics to the reaction force characteristics Mb formaintaining the sense of initiative by performing the minute change suchthat the reaction force increase amount with respect to the increase ofthe pedal stroke of the brake pedal in the appropriate brake operationamount range Eb is large compared to that in the reference reactionforce characteristics Bb. In the reaction force characteristics Mb formaintaining the sense of initiative, the reaction force increase amountwith respect to the increase of the pedal stoke in the appropriate brakeoperation amount range Eb is large compared to the reaction forceincrease amount (the reaction force increase amount along the referencereaction force characteristics Bb) with respect to the increase of thepedal stoke from the brake operation amount at the time of determinationthat the pedal stroke of the brake pedal by the driver is not includedin the appropriate brake operation amount range Eb to the time when thepedal stroke reaches the appropriate brake operation amount range Eb.

In the reaction force characteristics Mb for maintaining the sense ofinitiative, in order to increase the slope in the appropriate brakeoperation amount range Eb compared to that in the reference reactionforce characteristics Bb, the slope becomes smaller in the range of thepedal stroke than the appropriate brake operation amount range Eb, butnot becomes a negative slope.

FIG. 7B is a graph illustrating the reaction force characteristics whenthe accelerator pedal is released. In FIG. 6B, as a precondition, thecurrent pedal stroke of the brake pedal is equal to or larger than theappropriate brake operation amount Pb and exceeds the appropriate brakeoperation amount range Eb. The driver needs to release the brake pedaland return the brake pedal to reach the appropriate brake operationamount Pb by the reaction force.

In the situation illustrated in FIG. 7B also, since it is determined bythe determination unit 18 that the driver's pedal stroke correspondingto the appropriate brake operation amount Pb is not included in theappropriate brake operation amount range Eb, the reaction forcecharacteristics change unit 19 changes the reaction forcecharacteristics of the brake pedal from the reference reaction forcecharacteristics Bb to the reaction force characteristics Mb formaintaining the sense of initiative.

The reaction force characteristics change unit 19 changes the reactionforce characteristics to the reaction force characteristics Mb formaintaining the sense of initiative by performing the minute change suchthat the reaction force decrease amount with respect to the decrease ofthe pedal stroke of the brake pedal in the appropriate brake operationamount range Eb is large compared to that in the reference reactionforce characteristics Bb. In the reaction force characteristics Mb formaintaining the sense of initiative, the reaction force decrease amountwith respect to the decrease of the pedal stoke in the appropriate brakeoperation amount range Eb is large compared to the reaction forcedecrease amount (the reaction force decrease amount along the referencereaction force characteristics Bb) with respect to the decrease of thepedal stoke from the brake operation amount at the time of determinationto the appropriate brake operation amount range Eb. That is, when thepedal stroke enters the appropriate brake operation amount range Eb, thereturn of the accelerator pedal becomes slow.

The reaction force decrease amount with respect to the decrease of thepedal stroke corresponds to the slope of the reference reaction forcecharacteristics Bb and the reaction force characteristics Mb formaintaining the sense of initiative in FIG. 7B. The reaction forcecharacteristics change unit 19 performs the minute change on thereaction force characteristics of the brake pedal to be the reactionforce characteristics Mb for maintaining the sense of initiative inwhich the slope in the appropriate brake operation amount range Ebbecomes approximately three times or twice as large as the referencereaction force characteristics Bb. In the minute change, anymagnification between 1.1 times to 5 times may be adopted. The reactionforce characteristics Mb for maintaining the sense of initiative is thereaction force same as the reference reaction force characteristics Bbin the appropriate brake operation amount Pb.

The reaction force control unit 20 controls the reaction force of theoperation device T based on the operation amount of the driverrecognized by the operation amount recognition unit 15 and the reactionforce characteristics of the operation device T. The reaction forcecontrol unit 20 transmits a reaction force command value that is fromthe operation amount of the driver and is according to the reactionforce characteristics of the operation device T to the PID controller 7.The reaction force control unit 20 controls the reaction force of theoperation device T by transmitting the command value corresponding tothe PID control from the PID controller 7 to the reaction force actuator8.

If the reference reaction force characteristics is set as the reactionforce characteristics of the operation device T, the reaction forcecontrol unit 20 controls the reaction force of the operation device T bytransmitting the reaction force command value that is from the operationamount of the driver and is corresponding to the reference reactionforce characteristics to the PID controller 7. In addition, if thereaction force characteristics for maintaining the sense of initiativeis set as the reaction force characteristics of the operation device T,the reaction force control unit 20 controls the reaction force of theoperation device T by transmitting the reaction force command value thatis from the operation amount of the driver and is according to thereaction force characteristics to the PID controller 7.

FIG. 8 is diagrams for explaining a functional outline of the drivingassistance apparatus 100. In FIG. 8 , a case of the steering device STwill be described as an example. (A) of FIG. 8 illustrates a predictionof the driver's appropriate steering amount. As illustrated in (A) ofFIG. 8 , the appropriate operation amount prediction unit 16 predictsthe appropriate operation amount using the driving behavior model fromthe operation history of the driver, the external environment, thevehicle state, and the like. (B) of FIG. 8 is a diagram illustrating thedriver's appropriate steering amount. As illustrated in (B) of FIG. 8 ,the appropriate steering amount (dashed line) at the prediction timepoint is predicted from the current steering amount of the driver (solidline).

(C) of FIG. 8 is a diagram illustrating the steering amount of thedriver (input) at the prediction time point. The steering amount of thedriver may be a steering angle or may be input as a steering torque. (D)of FIG. 8 is a diagram illustrating the reaction force characteristicsfor maintaining the sense of initiative set by the virtual model. Here,it is assumed that the reaction force characteristics of the steeringdevice ST has already been changed to the reaction force characteristicsfor maintaining the sense of initiative. The reaction force control unit20 transmits the reaction force command value that is from the operationamount of the driver illustrated in (C) of FIG. 8 and that is accordingto the reaction force characteristics for maintaining the sense ofinitiative illustrated in (D) of FIG. 8 to the PID controller 7. The PIDcontroller 7 transmits a command value corresponding to the PID controlto the reaction force actuator 8 (steering reaction force actuator).

(E) of FIG. 8 is a diagram illustrating a state in which the reactionforce is given to the steering device ST and cooperates with the driver.As illustrated in (E) of FIG. 8 , the reaction force control unit 20controls the reaction force of the steering device ST by controlling thereaction force actuator 8 via the PID controller 7. The reaction forcecontrol unit 20 performs the reaction force control in cooperation withthe driver by performing the control of the reaction force actuator 8according to the reaction force characteristics for maintaining thesense of initiative in combination with the steering amount of thedriver. The driver makes the steering amount easy to stay in theappropriate steering amount range Es by receiving the reaction forceaccording to the reaction force characteristics for maintaining thesense of initiative.

The driver can continuously maintain the sense of initiative for thedriving operation almost without change in force sensing owing to thereaction force control by the driving assistance apparatus 100.

Processing by Driving Assistance Apparatus

Next, the processing by the driving assistance apparatus 100 in thepresent embodiment will be described with reference to the drawings.FIG. 9 is a flowchart illustrating an example of the reaction forcecharacteristics change processing. The reaction force characteristicschange processing illustrated in FIG. 9 is performed, for example, whenthe vehicle is traveling.

As illustrated in FIG. 9 , as S10, the ECU 10 of the driving assistanceapparatus 100 determines whether or not the vehicle is traveling on acurve using the curve traveling recognition unit 14. The curve travelingrecognition unit 14 determines whether or not the vehicle is travelingon the curve based on the curvature of the traveling road recognized bythe external environment recognition unit 12. If it is not determinedthat the vehicle is traveling on the curve (NO in S10), the ECU 10 endsthe current processing. The ECU 10 repeats the processing from S10 againafter a certain time has elapsed. If it is determined that the vehicleis traveling on the curve (YES in S10), the ECU 10 makes the processproceed to S12.

In S12, the ECU 10 performs the prediction of the appropriate operationamount using the appropriate operation amount prediction unit 16 andsetting of the appropriate operation amount range using the appropriateoperation amount range setting unit 17. The appropriate operation amountprediction unit 16 predicts the appropriate operation amount of thedriver based on the operation history of the driver stored in theoperation history storage unit 6, the external environment recognized bythe external environment recognition unit 12, and the vehicle staterecognized by the vehicle state recognition unit 13. The appropriateoperation amount range setting unit 17 sets the appropriate operationamount range that is a range set in advance including the appropriateoperation amount.

In S14, the ECU 10 determines whether or not the operation amount of thedriver corresponding to the prediction time point for the appropriateoperation amount is included in the appropriate operation amount rangeusing the determination unit 18. The determination unit 18 performs thedetermination described above based on the operation amount of thedriver recognized by the operation amount recognition unit 15 and theappropriate operation amount range set by the appropriate operationamount range setting unit 17. If it is determined that the operationamount of the driver corresponding to the prediction time point for theappropriate operation amount is included in the appropriate operationamount range (YES in S14), the ECU 10 ends the current processing. Inthis case, the reaction force characteristics of the operation device Tremains the reference reaction force characteristics. The ECU 10 repeatsthe processing from S10 again after a certain time has elapsed. If it isdetermined that the operation amount of the driver corresponding to theprediction time point for the appropriate operation amount is notincluded in the appropriate operation amount range (NO in S14), the ECU10 makes the process proceed to S16.

In S16, the ECU 10 changes the reaction force characteristics of theoperation device T to the reaction force characteristics for maintainingthe sense of initiative using the reaction force characteristics changeunit 19. The reaction force characteristics change unit 19 can changethe reaction force characteristics to the reaction force characteristicsfor maintaining the sense of initiative, for example, by a minute changefrom the reference reaction force characteristics. Thereafter, the ECU10 ends the processing.

Next, the reaction force control processing by the driving assistanceapparatus 100 will be described. FIG. 10 is a flowchart illustrating anexample of the reaction force control processing. The reaction forcecontrol processing is performed when the change to the reaction forcecharacteristics for maintaining the sense of initiative is performed inin S16 in FIG. 9 . The description for the case where the reaction forcecharacteristics remain as the reference reaction force characteristicswill be omitted.

As illustrated in FIG. 10 , as S20, the ECU 10 recognizes the operationamount of the driver using the operation amount recognition unit 15. Theoperation amount recognition unit 15 recognizes the operation amount ofthe driver for the operation device T of the vehicle based on theoperation amount information from the driving operation detection unit4.

In S22, the ECU 10 calculates the reaction force command value accordingto the reaction force characteristics for maintaining the sense ofinitiative using the reaction force control unit 20. The reaction forcecontrol unit 20 calculates the reaction force command value based on theoperation amount of the driver recognized by the operation amountrecognition unit 15 and the reaction force characteristics.

In S24, the ECU 10 transmits the reaction force command value to thereaction force actuator 8 using the reaction force control unit 20. Thereaction force control unit 20 controls the reaction force of theoperation device T by transmitting the command value to the reactionforce actuator 8 via the PID controller 7.

According to the driving assistance apparatus 100 in the presentembodiment described above, when it is determined that the operationamount of the driver amount corresponding to the prediction time pointfor the appropriate operation amount is not included in the appropriateoperation amount range, it is possible to make the operation amount ofthe driver stay in the appropriate operation amount range by changingthe reaction force characteristics to the reaction force characteristicsfor maintaining the sense of initiative in which the operation amount ofthe driver is likely to remain in the appropriate operation amount rangeby performing the minute change on the reaction force characteristics ofthe operation device.

The driving assistance apparatus 100 changes the reaction forcecharacteristics of the operation device to the reaction forcecharacteristics for maintaining the sense of initiative such that thereaction force increase amount with respect to the increase of operationamount in the appropriate operation amount is large compared to thereaction force increase amount with respect to the increase of theoperation amount from the operation amount at the time of determinationto the appropriate operation amount range. In this case, since thereaction force increase amount with respect to the increase of theoperation amount becomes large when the operation amount of the driverenters the appropriate operation amount range, it is possible to preventthe driver from increasing the force required for further operation andcausing the operation amount of the driver to exceed the appropriateoperation amount range, and thus, it is possible to make the operationamount of the driver easy to stay in the appropriate operation amountrange.

In addition, in the driving assistance apparatus 100, when it isdetermined that the operation amount of the driver amount correspondingto the prediction time point for the appropriate operation amount is notincluded in the appropriate operation amount range, the drivingassistance apparatus 100 changes the reaction force characteristics ofthe operation device to the reaction force characteristics formaintaining the sense of initiative such that the reaction forcedecrease amount with respect to the decrease of operation amount in theappropriate operation amount is large compared to the reaction forcedecrease amount with respect to the decrease of the operation amountfrom the operation amount at the time of determination to theappropriate operation amount range. In this case, since the reactionforce decrease amount with respect to the decrease of the operationamount becomes large when the operation amount of the driver enters theappropriate operation amount range, and the reaction force that booststhe operation amount of the driver decreases, it is possible to preventthe operation amount of the driver from exceeding the appropriateoperation amount range, and thus, it is possible to make the operationamount of the driver easy to stay in the appropriate operation amountrange.

Furthermore, in the driving assistance apparatus 100, since it is easyfor the operation amount of the driver to stay in the appropriateoperation amount range by changing the reaction force characteristics ofthe operation device, it is possible to maintain the sense of initiativeof the driver compared to the case where the operation amount of thedriver is forcibly interfered so as to become the appropriate operationamount. Therefore, driving assistance apparatus 100, it is possible toperform the driving assistance such that the operation amount of thedriver can be appropriate while maintaining the sense of initiative ofthe driver. As a result thereof, according to driving assistanceapparatus 100, the driving assistance can be performed such that theoperation amount of the driver becomes appropriate by the minute forcesensing interaction which does not impair the sense of initiative of thedriver, and thus, the driver has a feeling that his driving skill isimproved, and it is possible to activate the driving behavior. Inaddition, it is possible to suppress the fluctuations in driver'soperation when traveling the same lane in multiple times (largedifference occurs in the operation amount for each traveling).

In addition, according to the driving assistance apparatus 100, when itis determined by the determination unit 18 that the steering amount ofthe driver corresponding to the prediction time point of the appropriatesteering amount is not included in the appropriate steering amountrange, and when it is determined by the curve traveling recognition unit14 that the vehicle is traveling on the curve, since the reaction forcecharacteristics of the steering device ST of the vehicle is changed tothe reaction force characteristics for maintaining the sense ofinitiative, it is possible to make the steering amount of the drivereasy to stay in the appropriate steering amount range when traveling onthe curve where the appropriate steering by the driver is required. Inaddition, in the driving assistance apparatus 100, since it is easy forthe steering amount of the driver to stay in the appropriate steeringamount range by changing the reaction force characteristics of thesteering device ST, it is possible to perform the driving assistancesuch that the steering amount of the driver becomes appropriate whilemaintaining the sense of initiative of the driver compared to the casewhere the steering amount of the driver is forcibly interfered so as tobecome the appropriate steering amount.

As described above, the preferred embodiment of the present disclosurehas been described, however, the present disclosure is not limited tothe embodiments described above. The present disclosure can beimplemented in various forms including various modifications andimprovements based on the knowledge of those skilled in the art,including the above-described embodiments.

The driving assistance apparatus 100 does not necessarily need to usethe PID controller 7. The ECU 10 may be directly connected to thereaction force actuator 8. In this case, the ECU 10 may have a feedbackfunction for suppressing the influence of disturbance instead of the PIDcontroller 7.

The driving assistance apparatus 100 does not necessarily need to usethe GPS receiver 1 and the map database 5. In this case, the ECU 10 doesnot need to include the vehicle position recognition unit 11. Theexternal environment recognition unit 12 may recognize the externalenvironment of the vehicle only from the result of detection performedby the external sensor 2.

The appropriate operation amount prediction unit 16 may predict theappropriate operation amount without using the vehicle state. In thiscase, the ECU 10 does not necessarily need to be connected to theinternal sensor 3, and the ECU 10 does not need to include the vehiclestate recognition unit 13. The appropriate operation amount may be anyoperation amount as long as the operation amount that is performed bythe driver corresponding to the external environment along the operationhistory of the driver.

The appropriate operation amount prediction unit 16 may predict theappropriate operation amount using the driver's driving trend. Thedriver's driving trend can be obtained from the operation history of thedriver using well-known evaluation technology.

The ECU 10 of the driving assistance apparatus 100 does not necessarilyneed to include the curve traveling recognition unit 14. If it isdetermined by the determination unit 18 that the operation amount of thedriver corresponding to the prediction time point for the appropriateoperation amount is included in the appropriate operation amount rangeregardless of whether the vehicle is traveling on the curve or not, thereaction force characteristics change unit 19 may change the reactionforce characteristics of the operation device T to the reaction forcecharacteristics for maintaining the sense of initiative.

The reaction force characteristics change unit 19 may change thereaction force characteristics for maintaining the sense of initiativeaccording to the driver's driving trend and/or the driving skill. Thedriver's driving trend and the driving skill can be obtained from theoperation history of the driver using well-known evaluation method. Inthe driver's skill, the characteristics (veteran characteristics,beginner characteristics, or the like) may be classified according to aresult of comparison between the operation history of the driver and thereference model operation. When the driving skill of the driver is theveteran characteristics, the reaction force characteristics change unit19 may decrease the slope in the appropriate steering amount range Es ofthe reaction force characteristics M for maintaining the sense ofinitiative in FIG. 3 and FIG. 4 compared to the case where the driver'sdriving skill is the beginner characteristics. For example, the slopemay be set approximately 2 times the slope of the reference reactionforce characteristics B when the driving skill of the driver is theveteran characteristics, and may be set to approximately three times thereference reaction force characteristics B when the driving skill of thedriver is beginner characteristics.

The reaction force characteristics change unit 19 does not necessarilyneed to set the reaction force characteristics for maintaining the senseof initiative using the reference reaction force characteristics. Thereaction force characteristics change unit 19 may set the reaction forcecharacteristics for maintaining the sense of initiative regardless ofthe reference reaction force characteristics.

The driving assistance apparatus 100 performs the driving assistancesuch that the steering amount of the driver becomes appropriate whilemaintaining the sense of initiative of the driver, however, it does notexclude the forcible operation interference depending on the situation.In a situation where it is necessary to avoid contact between thevehicle and an object, the driving assistance apparatus 100 may performthe operation interference for forcibly changing the operation amount ofthe driver. The driving assistance apparatus 100 may determine whetherthere is a possibility of contact between the vehicle and the object,and may perform the change to the reaction force characteristics formaintaining the sense of initiative when it is determined that there isno possibility of contact.

What is claimed is:
 1. A driving assistance apparatus that is configuredto assist a driving operation of a vehicle by a driver, comprising: anelectronic control unit (ECU) including a processor programmed to:recognize an operation amount of the driver for an operation device ofthe vehicle; recognize an external environment of the vehicle; predictan appropriate operation amount which is the operation amount, at aprediction time point after a current time point, performed by thedriver in correspondence with the external environment, based on theexternal environment; set an appropriate operation amount rangeincluding the appropriate operation amount when the appropriateoperation amount is predicted; determine whether the operation amount ofthe driver corresponding to the prediction time point of the appropriateoperation amount is included in the appropriate operation amount range;and change reaction force characteristics of the operation device suchthat a reaction force increase amount with respect to the increase ofthe operation amount in the appropriate operation amount range is largecompared to the reaction force increase amount with respect to theincrease of the operation amount from the operation amount at the timeof the determination to the appropriate operation amount range, or suchthat the reaction force decrease amount with respect to the decrease ofthe operation amount in the appropriate operation amount range is largecompared to the reaction force decrease amount with respect to thedecrease of the operation amount from the operation amount at the timeof the determination to the appropriate operation amount range, when itis determined that the operation amount of the driver corresponding tothe prediction time point of the appropriate operation amount is notincluded in the appropriate operation amount range.
 2. The drivingassistance apparatus according to claim 1, wherein the ECU is furtherprogrammed to: recognize a steering amount of the driver for a steeringdevice of the vehicle as the operation amount of the driver for theoperation device, predict an appropriate steering amount as theappropriate operation amount, set an appropriate steering amount rangeas the appropriate operation amount range, determine whether thesteering amount of the driver corresponding to the prediction time pointof the appropriate steering amount is included in the appropriatesteering amount range, and change the reaction force characteristics ofthe steering device, such that the reaction force increase amount withrespect to the increase of the steering amount in the appropriateoperation amount range is large compared to the reaction force increaseamount with respect to the increase of the steering amount from thesteering amount at the time of the determination which is the steeringamount at the time of determination to the appropriate operation amountrange, or such that the reaction force decrease amount with respect tothe decrease of the steering amount in the appropriate steering amountrange is large compared to the reaction force decrease amount withrespect to the decrease of the steering amount from the steering amountat the time of the determination to the appropriate steering amountrange, when it is determined that the steering amount of the drivercorresponding to the prediction time point of the appropriate steeringamount is not included in the appropriate steering amount range.
 3. Adriving assistance apparatus that is configured to assist a drivingoperation of a vehicle by a driver, comprising: an electronic controlunit (ECU) including a processor programmed to: recognize an operationamount of the driver for an operation device of the vehicle; recognizean external environment of the vehicle; predict an appropriate operationamount which is the operation amount, at a prediction time point after acurrent time point, performed by the driver in correspondence with theexternal environment, based on the external environment; set anappropriate operation amount range including the appropriate operationamount when the appropriate operation amount is predicted; determinewhether the operation amount of the driver corresponding to theprediction time point of the appropriate operation amount is included inthe appropriate operation amount range; and change a reaction forcecharacteristics of the operation device to a reaction forcecharacteristics for maintaining the sense of initiative with which theoperation amount of the driver amount can easily remain in theappropriate operation amount range by performing a change on thereaction force characteristics of the operation device when it isdetermined that the operation amount is included in the appropriateoperation amount range, when it is determined that the operation amountof the driver corresponding to the prediction time point of theappropriate operation amount is not included in the appropriateoperation amount range.
 4. The driving assistance apparatus according toclaim 3, wherein the ECU is further programmed to: determine whether thevehicle is traveling on a curve, recognize a steering amount of thedriver for the steering device of the vehicle as the operation amount ofthe driver for the operation device, predict an appropriate steeringamount as the appropriate operation amount, set an appropriate steeringamount range as the appropriate operation amount range, determinewhether the steering amount of the driver corresponding to theprediction time point of the appropriate steering amount is included inthe appropriate steering amount range, and when it is determined by thedetermination unit that the steering amount of the driver correspondingto the prediction time point of the appropriate steering amount is notincluded in the appropriate steering amount range and when it isdetermined that the vehicle is traveling on the curve, change thereaction force characteristics of the steering device to the reactionforce characteristics for maintaining the sense of initiative.